Reheater



Feb. 7, 1933. w ARMACOST 1,896,213

'REHEATER Filed Oct. 31. 1951' 3 Sheets-Sheet 1 Fig.1

INVENTOR mzm ATTORNEY Wi lbw H. Exma o i' REHEATER Filed Oct. 31. 1951 5 Sheets-Sheet 2 E E E E E E E E E E E E E E E E E E ATTORNEY Feb; 7, 1933. I H. ARMACOST 1,896,213

REHEATER Filed Oct. 31, 1931 5 Sheets-Sheet 3' I INVENTOR.

\A r I bur H. Anna/c 319,

A TTORNE Y.

Patented Feb. 7, 1933 UNITED STATES,

PATENT OFFICE- WILBUB. n. ARMACOST, or new YORK, 1 I. Y., ,AssIGnon TO THE SUPERHEATER COMPANY, or new on-x, N. Y,

REHEATER I The present invention relates to the art of heat exchanger Heat exchangers for reheating steam and like purposes are in common use which have ashell through which the fluid to be heated passes and which have heating coils within the shell. Such heaters are compact and,

' when used as steam reheaters, avoid carrying large steam mains from the prime mover to lo the boiler furnace and back. Since, how-' ever, it is usually desired that the steam, or other fluid to be heated, make more than one pass in the heater, the shell of the ordinary form of such heater is subject to stresses caused by unequal thermal expansion due to the higher temperature of the fluid being heated in the outgoing pass over that in the incoming pass.

It is an object of my invention to provide an arrangement adapted to minimize stresses from thermal expansion. 1

A further object of my invention is'to provide a novel form of coil unit for use in steam heated heat exchangers.

u The novel features of my invention are pointed out in the appended claims. The invention itself, however, together with its objects and advantages, will best be understood from a detailed description of two forms of heat exchanger selected byway of example from a number of possible embodi ments of the invention, and such a description will now be given in connection with the accompanying drawings in Which-'- Fig. 1 is a longitudinal sectional view, parts being broken away, of an apparatus within my invention.

Fig. 2 is a section taken on the line 2-2 of 2 looking in the direction of the arrows.

Fig. 3 is a longitudinal sectional viewof a second form of heat exchanger within my invention.

Fig. 4 is a section taken on the line 4& of Fig. 3, looking in the direction of the arrows.

Fig. 5 is a detail of a portion'of one of the heating units illustrated in Figs. 3 and 4. .50 Fig. 6 is a View similar to Fig. .5 but includment shown for this purpose, the pass 26 has ing also a portion of the supports for the heating unit. y 1

Fig. 7 is a view of a portion of a heating unit taken at rightangles to Figs. .5 and 6. r

Fig. 8 is a top view of a portion ofthe unit shown in Fig. 7.

The apparatus illustrated in Fig. 1 comprises .a cylindrical shell lOhaving an inlet 12 near its upper end for fluid to be heated and an outlet 14 for such fluid somewhat below inlet 12. In the arrangement shown,

fluid passing inwardly through. opening 12 enters a chamber .16 which is enclosed by the upper end or head 18 of the shell, the vertical wall 20 and horizontal plate 22 as well as a portionv of the cylindrical wall of the shell 10. Fluid passes-out of chamber 16 through an opening in the wall 20, a steam separator 24 of known type being placed on the oppo- "I site side of wall 20'fro1n chamber 16 toact on fluid going therefrom.

Horizontal plate 22 extends across the bot tom of chamber 16 and some distance beyond the wall 20 and forms the top ofa central up-, 7 5; pass 26 within shell 10 which has a poly'zgonal, preferably square, section, defined by walls 28, 28a. Pass 26 is open at the bottom to re-- ceive. fluid to be heated which rises therethrough to the level of the outlet 14. Outlet 14, as clearly appears in Fig. 1, leads out of the upper end of pass .26; The separator 24 beingn'ear the top of shell 10 andthe lower end of thepass 26 being near the lower end thereof, the ingoing relatively. coolfluid from the outlet of separator 24 flows downwardly through the shell to enter pass 26. In order to avoid, as far as possible,unequal thermal expansion and the stresses produced thereby, it is desirable that the flow of fluid within shell 10 be as symmetrical as possible. For this purpose I have arranged thatthe rela: tively cool liquid contactthe shell 10 around its entire cylindrical portion. In the arrange a cross section in the form of a polygon, preferably square, whose corners are internally in contact with the surface of shell 10 and lie parallel to the longitudinal axis of such shell. This arrangement isshown in dotted 9 lines in Fig. 2 and is better illustrated in Fig. 4, this feature being common to both the form illustrated in Figs. land 2 and that illus-. trated in Figs. 3 and 4. By this arrangement, the wall of pass 26 forms three similar longitudinal passages 30, 30 of similar segmental cross section, and a'fourth segment 30 whose chord wall is shown at 28a. In the arrangement shown in Figs. 1 and 2 the fluid from separator 24 can pass directly downward through one of the passages 30 lying opposite the inlet 14 andcan pass around the top and ends of the separator 24 to the top of the passages 30 which have their plates28 parallel to the axis of outlet 14. The segmental passage sea on the same side of the shell is closed by the plate 22 at the top, but is filled with steam or like fluid being heated which passes around the lower edges of the plates 28 and 28a and which is of substantially the same temperature as that in passages 30.

Elements for heating the fluid in' pass 26 are shown at 34. Steam, or like heating fluid, for elements 34 may be introduced into the shell 10 through the header 32 which has heating elements 34 connected thereto in any known or preferred manner. The heating elements 34 extend up into the pass 26 and heat the fluid which passes therethrough in contact with the exterior of the elements in the usual manner. Elements 34 may have their other ends connected to a discharge header not shown) similar to header 32 or they may be so arranged that the condensate will drain back through header 32.

In the arrangement illustrated in Figs. 3 and4 the cylindrical shell 10a has a partition 28?) therein arranged to form an up-pass 26a having a polygonal cross section. As illustrated, partion 287) is arranged to give the pass 26a asquare cross section, the transverse cross section of the partition forming a square circumscribed within shell 10a and whose corners are welded or otherwise secured thereto along lines parallel to the axis of the shell. Partition 28b therefore forms, together with the shell 10a, chambers of segmental cross section extending longitudinally of the shelllOa on the outside of the partition 286, Two of such segments are designated in Figs. 3 and 4 by reference character 30a, 30a and two other such segments are designated by ref erence character 30?), 30?). The upper end of pass 26a is open-so that fluid may pass around the upper edge of the partition 28?) into the chambers 30a whichare used together as a down-pass. Fluid to be heated is introduced intothe heat exchanger shown in Figs. 3 and 4-thru inlet 12a which passes thru shell 10a and delivers into the up-pass =26a'thru partition 28?). The fluid to be heated thereupon. travels up thru the pass 26a and down thru passages 30a and discharges from the shell thru the outlet 14a, which is preferably about on the same level'as the inlet 12a, both inlet pass between the lower end of'the pass 26a and theend or head 18 of the shell and thence somewhat upwardly thru the lower end of the other passage 30a and into the outlet 14a. As shown, pass 26a is closed at its bottom by plate 64 to form a passage 31 to connect the chambers 30a in the manner just described. The segmental chambers 30?) are closed at their lower ends by plates (not shown).

The fluid which enters the heat exchanger of Figs. 3 and 4 thru inlet 12a is heatediiu' pass 26a by a tube bundle T. Bundle T- is composed of units one of which is illustrated in part in Figs. 5 and 6, each unit having two elements 34a therein, parts of which are of 7 serpentine form, portions of the serpentine partsof one such element being shown on an enlarged scale in Figs. 7 and 8. Heating fluid such as steam or the like for bundle T is introduced thru shell 10a by an inlet header 32a. Each element 34a has an inlet section. 34?; which is connected so as to receive heating fluidfrom header 32d. Each element 34a also has an outletsection 34c connected to deliver fluid to'an outlet header 33a whereby usedheating fluid is discharged thru the shell 10a. The elements 34a are bifurcated at the points 70,- 71 near their tops and bottoms respectively; The sections 346 and 340 between the headers and points 70 and 71 respectively have equal diameters and are sufficiently larger than the individual pipes used intermediate points 70 and 71 so that the inlet sections 34?) and outlet sections 340 have approximately twice as 'much cross sections as the indivldual pipes of the elements intermediate suchpoints, each -element having, however, the same total cross sectional area throughout. The bifurcated portions of elements 34a, which are also the parts of serpentine form. consist of straight pipe runs 60a connected by return bends some of which are of the welded type, as

shown at 58, while others are of the plain type, as indicated at 66 and 67 The inlet sections or portions 34?) extend. upwardly along the partition 28b to the top of bundle T and the serpentine portions of the elements thereupon conduct the heating fluid downwardly to the outlet portion 340. Elements 3460 have a form which minimizes the number of welded bends 58and utilizes fully the one end of the given serpentine part, bends 66, 66 curve in the horizontal direction and the two parts of a given bifurcated tube lie one above the other, whereas at the other end of the serpentine the bends 58 and 67 lie in the same vertical plane, the two parts of the bifurcated tube of a given element being arranged so that the bends 58 and 67 come one within the other. As shown, the inner bend 58 of such a pair is formed advantageously by welding the ends of adjacent tube runs 60a.

The arrangement of the serpentine portions of two elements 34a to form a unit for insertion andremoval in shell 10a is best illustrated in Figs. 5 and 6. It will be clear from these figures that two pairs of hangers 48a and two beams 44a are combined with two elements 34a to form a unit for suspension in the pass 26a.

Also, as appears clearly in Figs. 3 and 4,

the two tube elements of each unit are placed face to face and interleaved so that one series of vertical bends 58 and 6'? of each element lies within the horizontal bends 66 of the other element of the same unit.

As appears clearly in Figs. 3 and 4, the inlet sections 34?) of each element 34a preferably run upwardly close to the partition 28?). As further appears from Fig. 4, some of sections 34?) are on the side of pass 26a adjacent one passage 30a and some on the side of the pass adjacent the other passage 30a. The section of the partition 285 between the up and down pass is thereby heated, and interchange of heat between the incoming and outgoing streams of fluid is thereby prevented. I prefer to use heating elements of the type illustrated in Figs. 3 and 4 in the apparatus of Figs. 1 and 2, but do not limit myself to this.

In the arrangement shown in Figs. 3 and l as well as in Figs. 1 and 2, the ends of shell 10a are closed by heads within which are manholes 68. 1

It will be seen that in Figs. 1 and 2, chambers 30 have substantially the same temperature throughout their lengths when in use and that the portions of the shell 10 covering such chambers are at substantially the same temperatures as the corresponding chord portions of partition 28, so that there is a minimum of thermally produced distortion and stress. I

The chamber 30", while having no flow therein, receives heat from the steam in pass 26 so that its shell portion and partition portion soon reach and maintain the same temperatures at given levels whereby the thermal stresses are minimized.

Similarly as to the arrangement of Figs. 3 and hthe wall portions of chamber 30a are all at substantially the same temperature throughout while in use and the wall portions of chambers 30?), while not entirely at uniform temperatures, have their temperaarrangement such that the fluid in certain of said segmentsmaintains the metal walls thereof at substantially the same temperature at given levels within the segment, heating elements within said polygonal pass, said segments each having communication with said polygonal pass at one end, and an inlet and an outlet connection, one to said poly onal 'pass and one to one of said segments.

2. The heat exchanger as set forthin claim 1 and in which the inlet and outlet are substantially at thesame level.

3. A heat exchanger having a cylindrical she'll and walls therein forming a central pass of polygonal cross section-the corners of which are parallel to the axis of said shell and securedthereto to form chambers of segmental cross section which connect withsaid olygonal pass and some of which are utiized as a second pass.

1. A heat exchanger having'a cylindrical shell and walls therein forming a pass of rectangular cross section, a tube bundle for heating fluid in said pass and having elements, each comprising inlet sections and,

outlet sections connected by bifurcated serpentine sections, some of said inlet sections extending along one side and some along the opposite side of said rectangularpass and said inlet and outlet sections entering said pass at the same end.

5. A coil element for heat exchangers having means at its ends for connection to headers, and an intermediate serpentine portion comprising parallel tubes having a series of coplanar reverse curves and a series of reverse curves in planes substant ally at right angles to said coplanar curves.

6. A coil element for heat exchangers having means at its ends for connection to head-' ers, and an intermediate serpentine portion comprising two parallel tubes having a series of coplanar reverse curves and. a serles of reverse curves in planes substantially at right angles to the planeof said coplanar curves, theinner ones of the coplanar curves comprising welded ends of adjacent tube runs. 7

7 A unit for heat exchangers comprising two elements each of which has means at its ends for connection to headers, and an intermediateserpentine portion comprising parallel tubes having'a series of coplanar reverse curves and a series of reverse curves in planes substantially at right angles to said coplanar its curves, the unit having the two elements interleaved so that the coplanar curves of one are embraced by non-coplanar curves of the other element. 7;

8. A heat exchanger as set forth in claim A and in which the two-segmental chambers between the rectangular pass and the shell of theexchanger which are on the same sides of said pass as the inlet and outlet sections 10 of the elements have connections with said rectangular pass at one end, and a connection with the exterior of the shell whereby they form a second pass.

9. A heat exchanger having a ,vertical shell, an inlet chamber within the upper end of said shell; a down-pass along the shell, an up-pass substantially central of said shell and connected to said down-pass, and an outlet connected to the upper end of said up pass for discharging heated fluid through the shell. 7 I r 10. A heat exchanger as set forth in claim 9 and in which a separator-is arranged to act on steam intermediate the inlet chamber and the down-pass. Y

' WILBUR H. ARMACOST.' 

